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ES 13 Geologic Time
Earth Science terms associated with dating fossils & Geologic Time
| Question | Answer |
|---|---|
| Its organization is based on (1)fossil life forms, (2)geologic events, and (3)environmental conditions | Geologic Time Scale |
| largest divisions on the Geologic Time Scale | eons (4) |
| 4 geologic eons (H.A.P.P.-Y) | Hadean, Archean, Proterozoic, Phanerozoic |
| shortest division on the Geologic Time Scale | epoch |
| when taken together, the first 3 eons (Hadean, Archean, Proterozoic) are collectively referred to as _?_ (time) | Precambrian |
| eras of the Phanerozoic Eon (P.ay M.e C.ash $$$) | Paleozoic, Mesozoic, Cenozoic |
| periods of the Phanerozoic Eon (C.an O.ld S.enators D.emand M.ore P.olitical P.ower T.han J.unior C.ongressmen? T.ough Q.uestion!) | Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, Permian, Triassic, Jurassic, Cretaceous, Tertiary, Quaternary |
| Epochs of the Cenozoic Era (P.ut E.ggs O.n M.y P.late P.lease H.oney) | Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, Holocene |
| determining age of fossil or geologic layer compared to another fossil or layer | relative age dating |
| principle that assumes Earth's geologic processes have always occurred in a similar way throughout time | Uniformitarianism |
| principle that assumes sedimentary rock was deposited in flat layers | Original Horizontally |
| principle that assumes that the oldest rocks are on the bottom of an undisturbed sequence of rocks | Superposition |
| principle that assumes an igneous intrusion or fault is younger that rocks it cuts through | Cross-Cutting Relationships |
| principle that assumes rock fragments (inclusions) are older than the rock layer that contains them | Inclusion |
| (principle that assumes) gap or irregularity in the rock record caused by erosion (or some other effect) | Unconformity |
| (principle that assumes) sediment beds and/or fossils from different areas can be matched up and assigned the same relative dates | Correlation |
| process that determines a specific number for how old a fossil or earth layer is | absolute age dating |
| using the breakdown of radioactive isotopes to determine the exact age of a fossil or rock | radiometric dating |
| time required for 50% of the radioactive atoms in a sample of radioisotopes to decay into a more stable (daughter) atom | half-life |
| radioactive isotope found in all plants and animals, having a half-life of 5730 years | carbon-14 (C-14) |
| rock type (igneous, sedimentary, metamorphic) for which radiometric dating is not very effective | sedimentary |
| absolute dating method that uses comparison of tree rings to date back up to about 10,000 years | dendrochronology |
| sample taken from ice caps or glaciers that contains atmospheric info from as much as 800,000 years ago | ice core |
| sedimentary layer deposited by meltwater from a glacier that may contain info that goes back in time over 100,000 years | varve |
| any preserved remains or traces of once-living organisms | fossil |
| fossilization that refers to plant or animals remains that have been altered very little since death (frozen, in amber, in tar, etc) | original preservation |
| fossilization that refers to plant or animal remains that have been preserved by exchanging original materials with chemicals such as silica | mineral replacement |
| fossilization that refers to preservation of plant/animal materials due to temperature and/or pressure altering the mineral structure but not composition | recrystallization |
| hollowed out impression left after a fossil weathers/decays | mold |
| fossil impression formed when material fills, then hardens in, a cavity left by a buried plant/animal when it decays | cast |
| indirect evidence (burrows, footprints, trails) left by past life (usually animals) | trace fossil |
| plant/animal remain that are easily recognized, were widely distributed, and existed for a relatively short time so its presence can be used to immediately identify the age of a layer | index fossil |
| the last epoch of geologic time that began about 12,000 years ago | holocene |
| the newly named epoch characterized by humans having a significant impact on Earth's environment and geology, its beginning defined by radioactive elements from nuclear bomb tests | anthropocene |
Created by:
goakley
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